datapath: Update the CT state key only after nf_conntrack_in().

datapath: Update the CT state key only after nf_conntrack_in().

Upstream commit:
    commit 394e910e909b174270b8231fd51942eb2f541fb9
    Author: Jarno Rajahalme <jarno@ovn.org>
    Date:   Thu Mar 10 10:54:19 2016 -0800

    openvswitch: Update the CT state key only after nf_conntrack_in().

    Only a successful nf_conntrack_in() call can effect a connection state
    change, so it suffices to update the key only after the
    nf_conntrack_in() returns.

    This change is needed for the later NAT patches.

    Signed-off-by: Jarno Rajahalme <jarno@ovn.org>
    Acked-by: Joe Stringer <joe@ovn.org>
    Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Jarno Rajahalme <jarno@ovn.org>
Acked-by: Jesse Gross <jesse@kernel.org>